1. Field of Invention
The present invention relates generally to network devices and to computer network systems which comprise network devices.
2. Background Information
Computer network systems, such as Local Area Networks (LANs), use network devices to interconnect nodes. Many computer network systems are implemented using Ethernet to provide a relatively high bandwidth interconnection of many nodes.
The nodes of a computer network system communicate using an established communication protocol to achieve point to point communication. Often, these protocols also include a multicast mechanism to send a data packet to multiple end nodes, and include a broadcast mechanism to send a data packet to all end nodes. This broadcast mechanism can limit the scaleability of a computer network system.
In addition to a broadcast mechanism, other techniques exist for directing a data packet to an end node. The virtual LAN (VLAN) standard allows for grouping nodes into Logical LAN groupings on a single fabric. In a VLAN environment, packets are assigned to a particular logical LAN and the packet is constrained to stay within that logical LAN. This ensures that unicast packets cannot be received outside of a particular grouping. Broadcast and multicast packets from a given node with a virtual LAN are similarly constrained to remain within the virtual LAN. The traffic containment that VLAN's provide, along with the controlled distribution of multicast packets, can permit a greater number of end nodes to be supported on a fabric. The IEEE VLAN standard has limited the length of a VLAN tag used to define the number of possible VLAN's within a computer network system to 12 bits.